Conversion of asphaliene-containing hydrocarbon charge stocks

ABSTRACT

Asphaltene-containing hydrocarbonaceous charge stocks, in slurry admixture with titanium tetrachloride, are reacted with hydrogen. The process may be effected with the titanium tetrachloride being composited with a refractory inorganic oxide carrier material, although the preferred mode of operation involves a slurry process with unsupported titanium catalyst of unknown constitution which results from titanium tetrachloride, admixed with the fresh charge stock, at reaction conditions in the presence of hydrogen and hydrogen sulfide.

' United States Patent 1 91 Gleim 1541 CONVERSION OF ASPHALIENE- CONTAINING HYDROCARBON CHARGE STOCKS [75] Inventor: William K. T. Gleim, Island Lake,

[73] Assignee: Universal Oil Products Company,

' Des Plaines, 111.

22 Filed: Au .30,1"9'71 [21] Appl.No.: 176,305

[52] U.S.Cl. .208/108, 208/44, 208/213, 252/441 [51] Int. Cl ..C10g 1/06,C10g/23/02 ClOglIi/QS [158] Field of, Search, ..208/108, 213, 44, 208/10; 252/441 [56] References Cited I UNITED STATES PATENTS 2,159,511 3 1939 Pier etal. ..208/108 2,191,156 2/1940 Pier et a1.

2,221,952 11/1940 Pier et al. ..208/10 1 1 Jan.30,1973

2,773,836 12/1956 Shalit et al ..252/437 2,865,841 12/1958 Hoekstra ..208/108 3,592,761 7/1971 Cole et a1. ..208/l08 3,668,109 6/1972 Kiovsky et 31.. ..208/10 3,258,418 6/1960 Pitchford et al ..208/44 Primary Examiner-Delbert E. Gantz Assistant Examiner-G. E. Schmitkons Attorney-James R. Hoatson, Jr. et a1.

57 ABSTRACT Asphaltene-containing hydroc'arbonaceous charge stocks, in slurry admixture with titanium tetrachloride, are reacted with hydrogen. The process may be effected with the titanium tetrachloride being composited with a refractory inorganic oxide carrier material, although the preferred mode of operation involves a slurry process with unsupported titanium catalyst of unknown constitution which results from titanium tetrachloride, admixed with the fresh charge stock, at reaction conditions in the presence of hydrogen and hydrogen sulfide.

4 Claims, N0 Drawings CONVERSION OF ASPHALIENE-CONTAINING HYDROCARBON CHARGE STOCKS APPLICABILITY OF INVENTION The invention described herein is adaptable to a 5 process for the conversion of asphaltene-containing petroleum crude oils into lower-boiling hydrocarbon products. More specifically, the present invention is directed towards a catalytic process for continuously converting atmospheric tower bottoms products, vacuum tower bottoms products, (vacuum residuum), crude oil residuum, topped crude oils, coal oil, oils extracted from tar sands, etc., all of which are sometimes referred to in the art as black oils, and which contain a significant quantity of asphaltenic material. In particular, the process described herein affords a high degree of asphaltene conversionto hydrocarbon-soluble products, while simultaneously effecting a substantial conversion of sulfurous and nitrogenous compounds to reduce the sulfur and nitrogen concentration.

Petroleum crude oils, particularly the heavy oils extracted from tar sands and vacuum residuum, contain high molecular weight sulfurous compounds in exceedingly large quantities. ln addition, these black oils contain excessive quantities of nitrogenous compounds, high molecular weight organo-metallic complexes principally comprising nickel and vanadium, and asphaltenic material. This asphaltic material generally found to'be complexed or linked with sulfur and to a certain extent with the organo-metallie contaminants. An abundant supply of such hydrocarbonaceous material currently exists, most of which has a gravity less than about 20.0API. This material is generally further characterized by a boiling range indicating that 10.0 percent by volume, and generally more, has a normal boiling point above a temperature of about 1,050F.

The process of the present invention is particularly 40 directed'toward the catalytic conversion of black oils into distillable hydrocarbons. Specific examples of black oils, illustrative of those to which the present invention is especially applicable, are a vacuum tower bottoms product, having a gravity of 7.lAPI, containtion affords the conversion of the greater proportion of such material, heretofore thought to be virtually impossible. The principal difficulty resides in the lack of a suitable technique which affords many catalytic composites the necessary degree of sulfur stability, while simultaneously producing lower-boiling products from the hydrocarbon-insoluble asphaltic material. This asphaltic materialconsists primarily of high. molecular weight non-distillable coke precursors, which are insoluble in light hydrocarbons such as pentane or heptane.

Heretofore, in the field of catalytic processing of such material, two principal approaches have been advanced: liquid-phase hydrogenation and vapor-phase, or mixed-phase hydrocracking. In the former type of process, liquid phase oil is passed upwardly, in admixture with hydrogen, into a fixed-fluidized catalyst bed. Although perhaps effective in converting at least a portion of the oil-soluble organometallic complexes, this type process is relatively ineffective with respect to the asphaltics. The retention of unconverted asphaltics, suspended in a free liquid phase oil for an extended period of time, results in polymerization and agglomeration. Some processes have been described which rely primarily upon cracking in the presence of hydrogen over a fixed-bed of a solid particulate catalyst. The latter rapidly succumbs to deactivation as a result of the deposition of coke and metallic contaminants thereon. Such a process requires an attendant high capacity regeneration system in order to implement the process on .a continuous basis. Briefly, the present invention involves a slurry-type process, utilizing titanium tetrachloride as the catalyst precursor, whereby the asphaltic material and catalyst are maintained in a dispersed state within a principally liquid phase rich in hydrogen. The asphaltic material is capa- 0 ble of intimate contact with the catalyst, thereby effecting reaction between hydrogen and asphaltic materials; the liquid phase is itself dispersed in a hydrogen-rich gas phase so that the dissolved hydrogen is continuously replenished.

In addition to asphaltenes, sulfurous and nitrogenous compounds, black oils contain greater quantities of metallic contaminants than are generally found in lighter hydrocarbon fractions. A reduction in the concentration of the organo-metallic contaminants, such as metal porphyrins is not easily achieved, and to the extent that the same no longer exert a detrimental effect with respect to further processing. When a hydrocarbon charge stock containing metals is subjected to a catalytic cracking process for the purpose of producing lower-boiling hydrocarbons, metals become deposited upon the catalyst employed, steadily increasing in quantity until such time as the composition of the catalytic composite is changed to the extent that undesirable results are obtained.

The principal object of the present invention is to provide a more efficient process for the hydrorefining conversion of heavier hydrocarbonaceous material containing insoluble asphaltenes. The term hydrorefining, as employed herein, connotes the catalytic treatment, in an atmosphere of hydrogen of a hydrocarbon fraction or distillate for the purpose of eliminating and/or reducing the concentration of the various contaminating influences previously described, accompanied by hydrogenation and significant conversion into lower-boiling hydrocarbon, products. As hereinabove set forth, metals are generally removed from the charge stock by deposition of the same onto the catalyst employed. This actively shields the catalytically active surfaces and centers from the material being processed, and thereby generally precludes the efficient utilization of a fixed-bed system. The present invention involves the use of a dissolved catalytic material in a slurry-type process. Although the catalyst precursor, titanium tetrachloride, may be composited with a suitable refractory inorganic oxide carrier material, a preferred technique involves unsupported titanium tetrachloride. The present process affords greater yields of a liquid hydrocarbon product which is more suitable for further processing without experiencing the difficulties otherwise resulting from the presence of the foregoing contaminating influences.

OBJECTS AND EMBODIMENTS One object of the present invention is to provide a more efficient process for the conversion of asphaltene-containing hydrocarbonaceous charge stock. A corollary objective is to provide a catalytic slurry-type process utilizing a colloidally dispersed titanium catalyst of unknown constitution.

Therefore, in a broad embodiment, the present invention involves a process for the conversion of an asphaltene-containing hydrocarbonaceous charge stock which comprises dissolving titanium tetrachloride in said charge stock and reacting the resulting mixture with hydrogen at hydrorefining conversion conditions. In another embodiment, the charge stock is reacted with hydrogen in the presence of about 2.0 percent to about 25.0 percent by weight of hydrogen sulfide, on the basis of the charge stock.

In a preferred embodiment, the titanium tetrachloride is dissolved in said charge stock in an amount from 0.5 percent to about 25.0 percent by weight, the actual catalytic agent being produced therefrom by the action of hydrogen, preferably in admixture with hydrogen sulfide.

SUMMARY OF INVENTION From the foregoing embodiments, it is readily ascertained that the process of the present invention involves the preparation of a catalytic agent within the hydrocarbonaceous charge stock from which the contaminating influences are to be removed. The catalytic agent is a titanium catalyst of unknown constitution which results from the titanium tetrachloride. Titanium tetrachloride may be used in combination with a suitable refractory inorganic oxide, including alumina, silica, zirconia, etc. In such a situation, the TiCl is generally impregnated thereon in an amount within the range of about 1.0 percent to about 30.0 percent by weight. Following impregnation, drying, and calcining, the impregnated carrier material is ground to a finelydivided state approximating 100/200 mesh. In a preferred mode of operation, the refractory carrier material is eliminated and the titanium tetrachloride is directly dissolved in the charge stock in an amount in the range of about 0.5 percent to about 25.0 percent by weight. Although increased quantities of titanium tetrachloride may be employed, they do not appear to significantly enhance the desired results.

One of the more common problems associated with catalysis by suspended, or colloidally dispersed, metals or compounds, is particle size. Decreasing particle size is the only practical means of increasing catalytically active surface since these particles have no internal, or interior, active surface. The only method available is to grind the solid catalytic agent to the smallest possible size; however, even such small particles still consist of many thousands of molecules bound together. The unique advantage of titanium tetrachloride as the catalyst precursor resides in its inherent miscibility with all hydrocarbon charge stocks; in other words, it is molecularly dispersed. Thus, the titanium tetrachloride, at reaction conditions, produces a catalyst which is a couple of orders of magnitude smaller than heretofore achieved.

It is believed that titanium tetrachloride is not the actual catalytic agent, but rather a unique precursor thereof. When the TiCl.,, in admixture with the charge stock, is subjected to the elevated operating conditions, in an atmosphere of hydrogen, reduction to some lower valence state occurs. As hereinafter indicated in specific examples, the addition of sodium to the TiCl /charge stock mixture, as a reducing agent, gave poorer results with respect to product gravity and Color Index. Hydrogen sulfide improved the conversion activity of titanium tetrachloride alone, as well as when in admixture with sodium. On the other hand, hydrogen sulfide did not improve the activity of titanium tetrachloride with magnesium.

Furthermore, I have shown that TiS is a poor conversion catalytic agent, and the activity is substantially unchanged upon the addition of sodium. However, the addition of hydrogen sulfide improves the activity. Thus, while the precise catalytic agent is not presently known with accuracy, it is believed to stem from the reaction of TiCl, with both hydrogen sulfide and the asphaltenic compounds to form a complex in which titanium has a valence less than 4 and the sulfur to titanium atomic ratio is greater than 2.0:1.0.

Briefly, the process is effected by initially admixing the desired quantity of titanium tetrachloride with the charge stock. The resulting mixture is then passed into a suitable reaction chamber maintained at a temperature within the range of about 225C. to about 500C. and under a hydrogen pressure of about 500 to about 5,000 psig. As hereinabove set forth, it appears that the presence of hydrogen sulfide in the hydrogen atmosphere, in an amount of 2.0 to 25.0 percent by weight of the charge stock, enhances the catalytic activity of the catalytic agent produced from the titanium tetrachloride. The process may be effected as a batchtype operation, or in a continuous manner in either upward flow, or downward flow. The normally liquid hydrocarbons are separated from the total reaction zone product effluent by any suitable means, for example, through the utilization of a centrifuge, or settling tanks, the remaining metal-containing sludge being treated as hereinafter set forth.

The metal-containing sludge is a viscous fluid consisting of the catalytically active metallic component, some unconverted asphaltic material, soluble hydrocarbons, porphyrinic material containing nickel, vanadium and other metallic contaminants, coke and heavy carbonaceous material, etc. Following separation of the normally liquid hydrocarbon product from the metal-containing sludge containing any unreacted titanium tetrachloride, the latter is recycled to combine with fresh charge stock. To maintain the catalytic agent in a steady-state operation, excess is withdrawn and treated with a suitable organic solvent for the purpose of dissolving residual organic-soluble material such as pentane-soluble hydrocarbon products resulting from the conversion of the insoluble asphaltenic compounds. Any well known organic solvent may be employed for the dissolution of the organic-soluble material in the sludge, and the resulting solution may be subjected to further reaction with hydrogen by recycling the same to combine with fresh hydrocarbon charge stock. The remainder of the sludge is then treated with a compound having the propensity to regenerate the titanium tetrachloride. Suitable compounds for this purpose include sulfur monochloride, sulfur dichloride, and their mixtures. The regeneration may be readily effected at a comparatively low temperature within the range of about 250C. to about 450C., the sulfur chlorides being employed in an amount from about 0.1 percent to about 25.0 percent by weight of the material to be treated, The sludge containing regenerated titanium tetrachloride is combined with the fresh hydrocarbon charge stock and reacted with hydrogen as aforesaid. In order to prevent a build up of coke, unconverted asphaltenic material and other carbonaceous residue, a controlled portion of the sludge will be withdrawn from the process and sent to a suitable metals recovery system.

The following examples are-presented to illustrate the process of the present invention and the effectiveness thereof in converting asphaltenic material. It is not intended that-the present invention be unduly limited to the method, charge stock and/or operating conditions employed in this illustration.

The charge stock was a vacuum tower bottoms having a gravity of 8.8API, containing 6.0 percent by weight of asphaltenic material, 3.0 percent by weight of sulfur, and 4,300 ppm. by weight of nitrogen; the 20.0 percent volumetric distillation temperature was 1,055F. The criteria employed to .indicate the degree of conversion, particularly with respect to asphaltenic material, was the Color Index of the product. Obviously, the lighter the color of the product, the lower the Color Index and the greater the degree of conversion. The Color Index was determined by UOP Method 707-71, based upon the information found in Analytical Chemistry, Vol. 34, pp. 694-700, 1962.

EXAMPLE I titanium tetrachloride were intimately commingled in a an 1,800 cc. rotating autoclave with hydrogen at a pressure of 100, atmospheres. Upon heating to a temperature of 400C., the pressure increased to about 200 at: mospheres. These conditions were maintained for a sixhour period, after which the autoclave was cooled and depressured, and the contents separated to provide a metal-containing sludge and the normally liquid product effluent. The latter was analyzed for Color Index and gravity, and in some instances forsulfur, nitrogen and asphalts. The first test was effected using 19 grams of titanium tetrachloride. A significant improvement was observed: the gravity increased from 8.8 to 27.8API and the Color Index was lowered from 150.0 to 2.6. When 10.0 grams of sodium were admixed with the TiCl, and charge stock, the results were not as beneficial; the gravity of the product was 20.5 API and the Color Index was 75.1.

Magnesium, in an amount of 5.5 grams, was commingled with 200 grams of charge stock and nineteen grams of titanium tetrachloride: again the results were not as acceptable as when TiCl was used above; the gravityv was 23.0 API and the Color Index was 14.0. Hydrogen sulfide, in an amount of 34.0 grams did not improve these results; the Color Index was 20.0 and the gravity was 20.0. When hydrogen sulfide, in an amount of 34 grams was admixed with charge stock, 19 grams of TiCl, and 10.0 grams of sodium, the gravity was about the same (as in the absence of H 8) at 20.2API, but the Color Index improved to a level of 26.6.

When 34 grams of hydrogen sulfide were added to the charge stock/TiCl, mixture, the gravity was increased to 32.8API and the Color Index dropped to 0.86.

EXAMPLE II Titanium disulfide was added to 200 grams of the charge stock, in an amount of ten grams; the gravity of the liquid product was 18.4 and the Color Index was 56.6. The addition of 8.5 grams of sodium did not change these results appreciably; the gravity was 17 .4API and the Color Index was 52.9. Some improvement, most noticeable in the Color Index, was achieved when H 5 (34 grams) was added to the 10.0 grams of titanium disulfide; the Color Index dropped to 23.2, but the gravity rose only to 19.5API.

It should be noted from the foregoing that no catalytic agent approached the results achieved through the use of TiCl, alone, or with added hydrogen sulfide.

EXAMPLE III The beneficial effect of added hydrogen sulfide was noticeable in an operation designed to check the effect of magnesium addition. The magnesium addition was based upon the expectation that the TiCl, and magnesium would result in titanium of reduced valence and magnesium chloride. When this reaction is effected simultaneously with black oil conversion, it is conceivable that the titanium tetrachloride undergoes reactions with the charge stock prior to reacting with the magnesium. To check this theory, 19 grams of titanium tetrachloride and 4.9 grams of magnesium were reacted in 50 grams of a white oil for six hours at atmospheres of hydrogen and C. A white oil is a heavy gas oil from which all contaminating influences have been removed. Following this pretreatment, 200 grams of black oil were added and the resulting mixture processed as previously 'set forth.

In 'the'absence ofhydrogen sulfide, the gravity was 24.4API, the Color Index' was 12.0 and the product contained 0.40 percent by weight of heptane-insoluble asphaltenes. In addition, the product contained 0.74 percent sulfur and 1,370 ppm. of nitrogen. With the addition of 34.0 grams of hydrogen sulfide, the gravity was 25.8API, the Color Index dropped to 39 and only 0.12 percent by weight of heptane-insoluble asphaltenes remained in the product; the nitrogen concentration had been decreased to a levelof 990 ppm. by weight.

The foregoing specification and examples indicate the method by which the present invention is effected and the benefits afforded through the utilization thereof.

that said charge stock is reacted with hydrogen in the presence of about 2.0 percent to about 25.0 percent by weight of hydrogen sulfide, based upon said charge stock. 

1. A process for the conversion of an asphaltene-containing hydrocarbonaceous charge stock which comprises dissolving titanium tetrachloride in said charge stock and reacting the resulting mixture with hydrogen at hydrorefining conversion conditions.
 2. The process of claim 1 further characterized in that said conversion conditions include a temperature from 225*C. to about 500*C. and a pressure in the range of 500 psig. to about 5,000 psig.
 3. The process of claim 1 further characterized in that said titanium tetrachloride is present in an amount from 0.5 percent to 25.0 percent by weight of said charge stock. 